The dump body mechanism design is very clever :
The hydraulic pump and the distributor are incorporated into the hydraulic cylinder body, thus avoiding any hydraulic hose. This way, the dump body can very easily be removed and replaced by any other standard GMC CCKW equipment.
Equipped with the dump body, the only two links with the truck chassis are :
– the small shaft coming from the gear box PTO (Power Take Off) and going to the hydraulic pump
– the linkage between the push/neutral/pull lever in the cab and the hydraulic distributor (raise, lower or maintain the dump body in position).
Additionally, the large diameter of the hydraulic cylinder entailed a rather low pressure thus allowing the use of ordinary engine oil, available everywhere (on the contrary, hydraulic oil was relatively uncommon at that time).